Plastic covered building structures

ABSTRACT

A plastic covered building structure comprised of a metal frame supporting superimposed layers of plastic sheets having an inflated area between the sheets providing insulation to the interior of the structure. The super-imposed plastic sheets are secured to the frame by means of longitudinally extending rails having longitudinally extending upwardly concave portions and complementary clamping rods adapted to secure the edges of the super-imposed plastic sheets between the rods and the upwardly concave portions of the rail. The rails are adapted to receive clamping members at any point along the length of the rails to clamp the rods into the upwardly concave portions.

1Jnited States Patent 91 Gahler Feb. 12, 1974 [5 PLASTIC COVEREDBUILDING 3,548,904 12/1970 Mackell 52/2 ST C S 3,664,069 5/1972 Ikai52/2 [75] Inventor: Charles C. Gahler, West Long Examiner john MurtaghBranch Attorney, Agent, or Firm-Albert C. Nolte, Jr.; Ed- 731 Assignee:x. s. Smith, Inc., Red Bank, NJ. ward Hunter; (1 Bruce Hamburg PP212,069 A plastic covered building structure comprised of a metal framesupporting superimposed layers of plastic 52 U.S.C1 52/2, 52/63, 135/3 RSheets inflatederea. between the Sheets 51 Int. Cl E041) 1/345 dinghehlamh the of the ehuehhe The [58] Field of Search..... 52/2, 63' 135/1R, 3 R, 5 R, euper'hhpeeed sheets are e e heme 135/7 1 by means oflongitudinally extending rails having longitudinally extending upwardlyconcave portions and [56] References Cited complementary clamping rodsadapted to secure the edges of the super-imposed plastic sheets betweenthe UNITED STATES PATENTS rods and the upwardly concave portions of therail. 2,4l 1,316 1l/l946 Capita The rails are adapted to receiveclamping members at 3,165,110 1/1965 Brooks 135/3 R any point along thelength of the rails to clamp the g; 52, rods into the upwardly concaveportions. 3,483,879 12/1969 Oehmsen 135/1 R 18 Claims, 10 DrawingFigures I INVENTOR (Memes CT 5/31/4513 ATTORNEYS PLASTIC COVEREDBUILDING STRUCTURES The present invention relates generally to plasticcovered building structures of a semi-permanent nature and moreparticularly to semi-permanent greenhouse structures particularly usefulon farms and nurseries.

Building structures of a semi-permanent nature covered by plastic sheetsare well known. These structures can generally be assembled anddisassembled easily and provide year-round shelter for plants, etc. Theframes for such structures may be constructed of wood or metal, metalframes being preferred because of the added strength and additional caseof assembly and disassembly. Where wooden or partly wooden frames areutilized the plastic sheet covering is usually fastened to the structureby nails. Such tears or punctures made in the plastic sheet by the nailsused for securing it to the frame are susceptible to being quicklyenlarged by the effects of wind, snow, and rain. However, it is wellknown to provide frames, particulary metal frames, with fastening meansfor securing the plastic sheets to the frames without ripping or tearingthe plastic sheet. In the patent to Oehmsen, US. Pat. No. 3,483,879,granted Dec. 16, 1969, such a fastening device is disclosed. Thefastening means of the patent is comprised of an elongated member havinga longitudinal recess and complementary key received therein to therebywedge the plastic sheet between the key and the recess to eliminate theneed for nailing, etc. The elongated member is drilled and tapped atspecific locations to thereby allow a clamping member to secure the keyin the recess. In assembling the structure according to the patent it isnecessary, in addition to working outside the structure to secure afirst plastic covering, to work within the structure to secure a secondplastic covering which is separated from the outside first covering bythe frame of the structure. The purpose of providing two sheets ofplastic material separated by an air space is to insulate the interiorof the structure. Although the utilization of metal frames and theplastic sheet fastening devices of the Oehmsen patent are an improvementin the construction of plastic covered building structures, the factthat it is necessary to position two separate plastic sheets, one on theinterior of the frame and one on the exterior, is still time consumingand assembly and disassembly of the structure requires much effort. s ii It is, therefore, a primary object of the present invention I toprovide an improvement in plastic covered building structures wherebythey can be more easily assembled than previous such structures andwherein the plastic securing means will not reduce the useful life ofthe structure.

The plastic covered building structure of the present invention iscomprised of a metal frame supporting superimposed layers of plasticsheets having an inflated area between the sheets to thereby provideinsulation to the structure. The superimposed plastic sheets are securedto the frame by means of longitudinally extending rails havinglongitudinally extending upwardly concave portions and complementaryclamping rods adapted to wedge the edges of the superimposed plasticsheets between the rods and the upwardly concave portions of the rail.The rails are provided with means for receiving clamping members at anypoint along the length of the rails for clamping the rods into theupwardly concave portions of the rail.

.tion;

The present invention will be described and understood more readily whenconsidered with the accompanying drawings, in which:

FIG. 1 is a partial perspective view of a plastic covered buildingstructure according to the present inven- FIG. 2 is an explodedperspective view of a rail member for fastening the plastic sheets tothe frame of the structure;

FIG. 3 is a partial end view of the rail member of FIG.

FIG. 4 is an exploded partial perspective view of a gable rail for usewith the building structure of the present invention;

FIG. 5 is a partially cut-away section of the building structure takenalong section line 5-5 of FIG. 1;

FIG. 6 is a partial view of the structure of FIG. 5 taken along the line66 of FIG. 5;

FIG. 7 is a cross-sectional view taken along line 7--7 of FIG. 6;

FIG. 8 is a partially cut-away section of the building structure takenalong section line 8-8 of FIG. 1;

FIG. 9 is a cross-sectional view taken along section line 9-9 of FIG. 8;and

FIG. 10 is a detailed view of the gable rail as seen in FIG. 9.

Referring now to the drawings, in FIG. 1 there is shown the frame,generally designated 10, of a greenhouse structure, the frame 10 havingbow shaped rafter members 12 spaced apart and positioned bylongitudinally extending purlins 14 secured to the rafter members bymeans of clamps 15. The rafter members and purlins are preferably formedof metal tubing to provide sufficient lightweight support for thestructure against atmospheric conditions. A ridge rail, generallydesignated 16, and a vent rail, generally designated 17, provide theuppermost and bottommost longitudinal support for the structurerespectively, and additionally secure the plastic covering to frame 10.

As best seen in FIGS. 2 and 3 the ridge rail 16, and also the vent rail17 which is similar and to which the following description also applies,is a generally boxlike extrusion having upwardly concave portions in theform of flanges 18 and 20 extending from sides 22 and 24 of the ridgerail 16. In upper surface 26 of the ridge rail, channel 28 is formedhaving longitudinally extending grooves 30 in walls 29 and 31 of thechannel, the opposing grooves 30 are staggered with respect to eachother and have a pitch identical to the pitch of bolt 32 to therebyaccept the bolt. Bolt 32 secures clamping member 34 or rail splicemember 36 to ridge rail 16 at any point on the ridge rail. The concaveportions of flanges 18 and 20 are serrated as at 38 so that whenserrated clamping rod 40 presses the plastic covering sheets 42 and 44into the concave portion of flanges l8 and 20 the plastic sheets areimmovably wedged therein. Clamping member 34 is provided with a slot 46so that it may be moved to clamp either one or both of the splines 40associated with ridge rail 16, as best seen in FIG. 6. Splicing member36 acts to splice together two rails in abutting relationship, as at 48,so that the length of the ridge rail may be selected as desired (seeFIG. 6). Longitudinally extending slot 50 is formed in the bottomsurface 52 of ridge rail 16 for the purpose of accepting a bolt andwasher for securing the ridge rail to the frame as hereinafterdescribed. Both the ridge rail 16 and the vent rail 17 are constructedin such a way as to make the extrusion thereof a relatively simplematter with the need for a minimum of post extrusion operations toprepare the rails for use.

Referring now to FIG. 4 there is shown a gable rail, generallydesignated 54, which is positioned at the ends of the structure (seeFIG. 1) for securing the end margins of plastic sheets 42 and 44 andsecuring the end of the plastic sheet 56 which is draped to cover theend of the structure. Gable rail 54 is generally in the shape of aU-shaped channel having upwardly concave portions in the form of flanges58 and 60 for accepting the end margins of the plastic sheets. Clampingrod 62, clamped into the concave portions of flanges 58 and 60 by meansof clamping member 64, secure the plastic sheets to gable rail 54.Clamping member 64 is fastened to gable rail 54 by means of bolt 66passing through drilled hole 68 in gable rail 54 and into tapped hole 69in the end rafter bow, as best seen in FIGS. 8, 9, and 10. Theconstruction of the gable rail 54 also permits the extrusion thereofwith a minimum of post extrusion operations.

FIG. 5 clearly shows the means whereby the ridge rail 16 and vent rail17 are fastened to frame of the building structure. Pipe splices 70connect the ends of two adjacent rafter members 12 at their junction atthe top of the structure, and also connect the bottommost portion of therafter members to posts 72 which ar sunk into the ground for support ofthe structure. The pipe splices 70 secure the pipes by means of nut andbolt assemblies 74 so that a space 76 is provided between the adjacentpipes. For securing the ridge and vent rails to frame 10 there areprovided bolts 78 extending through openings 76 and slot 50 in the ridgeand vent rails to clamp surface 52 of the rails to pipe splices 70 bythe tightening of nut 80, as clearly seen in FIG. 7. FIG. 5 also showsthe spaced apart relationship of plastic sheets 42 and 44 after assemblyof the structure and after inflation of the space intermediate sheets 42and 44, by conventional means. This space intermediate sheets 42 and 44provides an effective insulation for the interior of the structure whilesimultaneously permitting sunlight to pass within. Inflation of thespace between plastic sheets 42 and 44 is made possible by the excellentsealing provided by the clamping of the edges of the plastic sheets bythe ridge, vent, and gable rails. The four corners of the plastic sheetswhich are not sealed by the various rails may be sealed by any knownmethod, as by heat sealing, etc. A wooden baseboard, generallydesignated 82, may be provided at the base of the structure forfinishing purposes and secured to posts 72 by means of nut and boltassemblies 84.

Referring to FIGS. 8 to 10 there is shown the end of the plastic coveredbuilding structure in detail. As can be seen in FIG. 8, gable rail 54 isbow shaped to conform to the shape of end rafter member 12 and issecured thereto by means of bolts 66 passing through holes 68 in gablerail 54 and into tapped holes 69 in end rafter member 12. For providinga covering for the open end of the structure, plastic sheet 56 isclamped to gable rail 54, as hereinbefore described, to drape over theend of the structure. For the purpose of providing gable frame members86, which may include a door frame as seen in FIG. 1, gable framebrackets 88 may be bolted to the end rafter member by bolt 89 and boltedto the gable frame members by means of bolt and nut assembly 90, asclearly seen in FIG. 9. The gable frame members 86 may be arranged inany configuration desired and have plastic sheet 56 secured thereto bymeans of nails or tacks 92.

In assembling the plastic covered building structure of the presentinvention the posts 72 are anchored in the ground in a spaced mannercorresponding to the position of the bow shaped rafter member 12. Thebow shaped rafter members 12 are spliced together by means of the pipesplices 70 and then raised to the upright position and spliced to posts72 by means of pipe splices 70, as best seen in FIGS. 5 and 8. Thepurlins 14 are then longitudinally positioned and secured to the raftermembers 12 by means of clamps l5. Ridge rail 16 and vent rail 17 arethen secured to frame 10 by means of the bolt washer assemblies 70, 80,as best seen in FIG. 5. In case the ridge or vent rails are notsufficiently long another rail may be positioned in abuttingrelationship and the two spliced together by means of splicing clamp 36,as best seen in FIGS. 2, 6, and 7. Gable rail 54 is then positioned onthe end rafter members with bolts 66 maintaining the position of thegable rails with respect to the rafter members. The building structureis now ready for the application of the plastic sheet covering.

Two superimposed sheets of plastic 42 and 44, large enough to coverone-half of the structure, are secured to ridge rail 16 by positioningthe top margin of the plastic sheets in the upwardly concave portion offlange 18 of the ridge rail and clamping rod into the concave portion bymeans of clamp 34, as clearly demonstrated in FIG. 3. The clamps 34 maybe positioned at any point along ridge rail 16 thereby providing asimple and easy method of clamping rod 40 in position. A similarprocedure is followed in fastening the lower margin of the superimposedsheets of plastic 42, 44 to the vent rail 17, as best seen in FIG. 5.The end margins of the superimposed sheets of plastic are secured to thegable rail 54 by positioning the end margin within the upwardly concaveportions of flanges 58 and 60 of the gable rail and clamping rod 62 intothe concave portions by means of clamps 64 which are secured by bolts66. The four corners of the superimposed plastic sheets are then sealed,thus making the space intermediate the plastic sheets air tight. Havingcompleted the securing of the plastic sheets 42 and 44 to the buildingstructure the space intermediate the superimposed sheets may then beinflated, by any conventional means, thereby spacing apart the centralportion of the superimposed sheets and providing an effective insulationfor the interior of the building. The remaining half of the structurewhich is uncovered may then be covered in a like manner as thatdescribed above to provide a completely covered structure.

The open ends of the structure may then be covered by positioning gableframe members 86 as necessary and securing them to the structure bymeans of gable frame brackets 88, as best seen in FIG. 8. A single sheetof plastic 56 may then be secured to the gable rail 54 in like manner asthe securing of the plastic sheets 42 and 44 to the gable rail. Theplastic sheet 56 is then draped over the end of the building and securedto the gable frame members 86 by means of nails or tacks 92.

It is understood that the foregoing general and detailed descriptionsare exemplary and explanatory of the present invention and are not to beinterpreted as restrictive of the scope of the following claims.

What is claimed is:

. relationship, a ridge rail secured to the tops of said rafter membersand extending the length of the building structure, said ridge railhaving top, bottom, and side surfaces, two upwardly concave portionsintegral with and oppositely disposed on either side of said ridge rail,two clamping rods, each of said rods received in one of said upwardlyconcave portions and extending the length thereof, means provided andoperative at any point along the length of said ridge rail top forclamping said rods into said upwardly concave portions, two superimposedplastic sheets secured along their top margin between one of theupwardly concave portions of the ridge rail and the complementary rod,means for securing the lower margin of the superimposed plastic sheetsto each other and to the structure, the central portion of saidsuperimposed plastic sheets being inflated to thereby space them apart.

2. The plasticcovered building structure as defined in claim 1 whereinthe means for clamping the rods into the upwardly concave portions ofthe ridge rail comprises a longitudinally extending channel in the topsurface of said ridge rail longitudinally extending grooves in theopposing interior vertical walls of said channel, the grooves in theopposing walls being in staggered relationship, at least one bolt havinga thread with an identical pitch as the grooves in said channel, and atleast one clamp secured to said ridge rail by said bolt and clampingsaid rods in the concave portions of the ridge rail, whereby said clampmay be secured to said ridge rail to clamp said rods at any positionalong the length of said ridge rail.

3. The plastic covered building structure as defined in claim 2 whereinthe means for securing the lower margin of the superimposed plasticsheets comprises a vent rail secured to the rafter members at a positionhorizontally below the ridge rail and extending the length of thebuilding structure, said vent rail having top, bottom, and sidesurfaces, and having an upwardly concave portion integral with and on atleast one side of the vent rail, a clamping rod received in the upwardlyconcave portion of said vent rail and extending the length thereof, andmeans for clamping said rod into said concave portion of said vent rail,the superimposed sheets of plastic being secured along their lowermargin between the concave portion of the vent rail and thecomplementary rod.

4. The plastic covered building structure as defined in claim 3 whereinthe means for clamping the rod into the concave portion of the vent railcomprises a longitudinally extending channel in the top surface of saidvent rail, longitudinally extending grooves in the opposing interiorvertical walls of said channel, the grooves in the opposing walls beingin staggered relationship, a bolt having a thread with an identicalpitch as the grooves in the channel, and a clamp secured to said ventrail by said bolt and clamping said rod in the concave portion of thevent rail, whereby said clamp may be secured to said vent rail to clampsaid rod at any po sition along the length of said vent rail.

5. The plastic covered building structure as defined in claim 2 whereinthe means for securing the end margins of the superimposed plasticsheets to each other andto the structure comprises a gable rail securedto the upper portion of each end rafter member, said gable rail havingan upwardly concave portion integral with and disposed on a side of saidgable rail, a clamping rod received in the concave portion of said gablerail, and means for clamping said rod into said concave portion, thesuperimposed sheets of plastic being secured along their end marginbetween the concave portion of the gable rail and the complementary rod.

6. The plastic covered building structure as defined in claim 3 whereinthe concave portion of the ridge rail and the vent rail are serrated andthe clamping rods received in the concave portions are also serrated.

7. The plastic covered building structure as defined in claim 3 whereinthe vent rail is secured to the lower parts of the rafter members by atleast one bolt passing through a longitudinally extending slot in thebottom surface of said vent rail, the head of the bolt engaging thebottom surface of the vent rail, said bolt being secured to the raftermembers.

8. The plastic covered building structure as defined in claim 7 whereinthe upwardly concave portion of the vent rail is formed in a flangeprotruding from a side surface of said vent rail.

9. The plastic covered building structure as defined in claim 8 whereinthe vent rail is extruded.

10. The plastic covered building structure as defined in claim 5 whichfurther comprises a sheet of plastic draped to cover the end of thebuilding structure, and means on said gable rail for securing the topmargin of said plastic sheet to said building structure.

11. The plastic covered building structure as defined in claim 10wherein said plastic sheet securing means comprises a second upwardlyconcave portion integral with and disposed on a side of said gable railopposite said first concave portion, a clamping rod received in thesecond concave portion of said gable rail, and means for clamping saidrod into said concave portion.

12. The plastic covered building structure as defined in claim 11wherein the concave portions of the gable rail are serrated and the rodsreceived in the concave portions are also serrated.

13. The plastic covered building structure as defined in claim 12wherein the gable rail is extruded.

14. The plastic covered building structure as defined in claim 12wherein the means for clamping the rods into the concave portions of thegable rail comprises openings in the top surface of said rail alignedwith tapped holes in the upper portion of the rafter member, boltsreceived through said openings and into said tapped holes, and clampssecured to said gable rail by said bolts and clamping at least one ofsaid rods in a concave portion of the gable rail.

15. A plastic covered building structure comprising a plurality ofrafter members positioned in spaced apart relationship, a ridge railsecured to the tops of said raf ter members and extending the length ofthe building structure, said ridge rail having top, bottom, and sidesurfaces, two upwardly concave portions integral with and oppositelydisposed on either side of said ridge rail, two clamping rods, each ofsaid rods received in one of said upwardly concave portions andextending the length thereof, means provided and operative at any pointalong the length of said ridge rail top for clamping said rods into saidupwardly concave portions, two superimposed plastic sheets secured alongtheir top margin between one of the upwardly concave portions of theridge rail and the complementary rod, means for securing the lowermargin of the superimposed plastic sheets to each other and to thestructure, the central portion of said superimposed plastic sheets beinginflated to thereby space them apart said ridge rail being secured tothe tops of the rafter members by at least one bolt passing through alongitudinally extending slot in the bottom surface of said ridge rail,the head of the bolt engaging the bottom surface of the ridge rail, saidbolt being secured to the rafter members.

16. The plastic covered building structure as defined in claim whereinthe upwardly concave portions of the ridge rail are formed in flangesprotruding from the side surfaces of said ridge rail.

17. The plastic covered building structure as defined in claim 16wherein said ridge rail is extruded.

18. A plastic covered building structure comprising a plurality ofrafter members positioned in spaced apart relationship, a ridge railsecured to the tops of said rafter members and extending the length ofthe building structure, an upwardly concave portion integral with saidridge rail, a clamping rod received in said upwardly concave portion andextending the length thereof, means provided and operative at any pointalong the length of said ridge rail top for clamping said rod into saidupwardly concave portion, two superimposed plastic sheets secured alongtheir top margin between said upwardly concave portion of said ridgerail and said clamping rod, means for securing the lower margin of thesuperimposed plastic sheets to each other and to the structure thecentral portion of said superimposed plastic sheets being inflated tothereby space them apart.

1. A plastic covered building structure comprising a plurality of raftermembers positioned in spaced apart relationship, a ridge rail secured tothe tops of said rafter members and extending the length of the buildingstructure, said ridge rail having top, bottom, and side surfaces, twoupwardly concave portions integral with and oppositely disposed oneither side of said ridge rail, two clamping rods, each of said rodsreceived in one of said upwardly concave portions and extending thelength thereof, means provided and operative at any point along thelength of said ridge rail top for clamping said rods into said upwardlyconcave portions, two superimposed plastic sheets secured along theirtop margin between one of the upwardly concave portions of the ridgerail and the complementary rod, means for securing the lower margin ofthe superimposed plastic sheets to each other and to the structure, thecentral portion of said superimposed plastic sheets being inflated tothereby space them apart.
 2. The plastic covered building structure asdefined in claim 1 wherein the means for clamping the rods into theupwardly concave portions of the ridge rail comprises a longitudinallyextending channel in the top surface of said ridge rail longitudinallyextending grooves in the opposing interior vertical walls of saidchannel, the grooves in the opposing walls being in staggeredrelationship, at least one bolt having a thread with an identical pitchas the grooves in said channel, and at least one clamp secured to saidridge rail by said bolt and clamping said rods in the concave portionsof the ridge rail, whereby said clamp may be secured to said ridge railto clamp said rods at any position along the length of said ridge rail.3. The plastic covered building structure as defined in claim 2 whereinthe means for securing the lower margin of the superimposed plasticsheets comprises a vent rail secured to the rafter members at a positionhorizontally below the ridge rail and extending the length of thebuilding structure, said vent rail having top, bottom, and sidesurfaces, and having an upwardly concave portion integral with and on atleast one side of the vent rail, a clamping rod received in the upwardlyconcave portion of said vent rail and extending the length thereof, andmeans for clamping said rod into said concave portion of said vent rail,the superimposed sheets of plastic being secured along their lowermargin between the concave portion of the vent rail and thecomplementary rod.
 4. The plastic covered building structure as definedin claim 3 wherein the means for clamping the rod into the concaveportion of the vent rail comprises a longitudinally extending channel inthe top surface of said vent rail, longitudinally extending grooves inthe opposing interior vertical walls of said channel, the grooves in theopposing walls being in staggered relationship, a bolt having a threadwith an identical pitch as the grooves in the channel, and a clampsecured to said vent rail by said bolt and clamping said rod in theconcave portion of the vent rail, whereby said clamp may be secured tosaid vent rail to clamp said rod at any position along the length ofsaid vent rail.
 5. The plastic covered building structure as defined inclaim 2 wherein the means for securing the end margins of thesuperimposed plastic sheets to each other and to the structure comprisesa gable rail secured to the upper portion of each end rafter member,said gable rail having an upwardly concave portion integral with anddisposed on a side of said gable rail, a clamping rod received in theconcave portion of said gable rail, and means for clamping said rod intosaid concave portion, the superimposed sheets of plastic being securedalong their end margin between the concave portion of the gable rail andthe complementary rod.
 6. The plastic covered building structure asdefined in claim 3 wherein the concave portion of the ridge rail and thevent rail are serrated and the clamping rods received in the concaveportions are also serrated.
 7. The plastic covered building structure asdefined in claim 3 wherein the vent rail is secured to the lower partsof the rafter members by at least one bolt passing through alongitudinally extending slot in the bottom surface of said vent rail,the head of the bolt engaging the bottom surface of the vent rail, saidbolt being secured to the rafter members.
 8. The plastic coveredbuilding structure as defined in claim 7 wherein the upwardly concaveportion of the vent rail is formed in a flange protruding from a sidesurface of said vent rail.
 9. The plastic covered building structure asdefined in claim 8 wherein the vent rail is extruded.
 10. The plasticcovered building structure as defined in claim 5 whiCh further comprisesa sheet of plastic draped to cover the end of the building structure,and means on said gable rail for securing the top margin of said plasticsheet to said building structure.
 11. The plastic covered buildingstructure as defined in claim 10 wherein said plastic sheet securingmeans comprises a second upwardly concave portion integral with anddisposed on a side of said gable rail opposite said first concaveportion, a clamping rod received in the second concave portion of saidgable rail, and means for clamping said rod into said concave portion.12. The plastic covered building structure as defined in claim 11wherein the concave portions of the gable rail are serrated and the rodsreceived in the concave portions are also serrated.
 13. The plasticcovered building structure as defined in claim 12 wherein the gable railis extruded.
 14. The plastic covered building structure as defined inclaim 12 wherein the means for clamping the rods into the concaveportions of the gable rail comprises openings in the top surface of saidrail aligned with tapped holes in the upper portion of the raftermember, bolts received through said openings and into said tapped holes,and clamps secured to said gable rail by said bolts and clamping atleast one of said rods in a concave portion of the gable rail.
 15. Aplastic covered building structure comprising a plurality of raftermembers positioned in spaced apart relationship, a ridge rail secured tothe tops of said rafter members and extending the length of the buildingstructure, said ridge rail having top, bottom, and side surfaces, twoupwardly concave portions integral with and oppositely disposed oneither side of said ridge rail, two clamping rods, each of said rodsreceived in one of said upwardly concave portions and extending thelength thereof, means provided and operative at any point along thelength of said ridge rail top for clamping said rods into said upwardlyconcave portions, two superimposed plastic sheets secured along theirtop margin between one of the upwardly concave portions of the ridgerail and the complementary rod, means for securing the lower margin ofthe superimposed plastic sheets to each other and to the structure, thecentral portion of said superimposed plastic sheets being inflated tothereby space them apart said ridge rail being secured to the tops ofthe rafter members by at least one bolt passing through a longitudinallyextending slot in the bottom surface of said ridge rail, the head of thebolt engaging the bottom surface of the ridge rail, said bolt beingsecured to the rafter members.
 16. The plastic covered buildingstructure as defined in claim 15 wherein the upwardly concave portionsof the ridge rail are formed in flanges protruding from the sidesurfaces of said ridge rail.
 17. The plastic covered building structureas defined in claim 16 wherein said ridge rail is extruded.
 18. Aplastic covered building structure comprising a plurality of raftermembers positioned in spaced apart relationship, a ridge rail secured tothe tops of said rafter members and extending the length of the buildingstructure, an upwardly concave portion integral with said ridge rail, aclamping rod received in said upwardly concave portion and extending thelength thereof, means provided and operative at any point along thelength of said ridge rail top for clamping said rod into said upwardlyconcave portion, two superimposed plastic sheets secured along their topmargin between said upwardly concave portion of said ridge rail and saidclamping rod, means for securing the lower margin of the superimposedplastic sheets to each other and to the structure the central portion ofsaid superimposed plastic sheets being inflated to thereby space themapart.